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Abstract The main object of this thesis was to research injection mouldable 0–3 type ceramic polymer composites and their dielectric and magnetic properties in the GHz frequency region. The work has been divided into three sections. In the first section, two–phase ceramic polymer composites containing dielectric and magnetic fillers have been investigated and their characteristics analysed by reference to pre–existing mixing rules. The exploitation of these composites in miniaturizing devices, such as antennae, is presented and discussed. The second part describes three phase composites containing different nanosize additives (silver, silicon and alumina fibres) towards improving their dielectric properties. In the third part, some periodical and multilayer structures for ceramic polymer composite layers are proposed. In the case of two–phase ceramic polymer composites, with 37 vol.% of dielectric filler (Barium Strontium Titanate, BST) embedded into a thermoplastic polymer (ER140) matrix, the highest measured relative permittivity was 15 with a dielectric loss value of 0.008 at 1 GHz. With 43 vol.% of magnetic filler (hexaferrite, CO2Z) in ER182 matrix, the highest achieved relative permeability was 1.8 with a magnetic loss value of 0.077 at 1 GHz. Composites with Co2Z filler provide a 77% size reduction, and could thus be used advantageously in antennae. It was found that a 2–6 vol.% nanoaddition in BST–ER140 composites enhanced the relative permittivity drastically with only a minor effect on the dielectric losses. In particular, with only 2 vol.% addition of nanosize silver particles into the BST–ER140 composite, a 52% increase in the relative permittivity was obtained, with no significant change in the dielectric losses (tan δε = 0.004). Vertically and horizontally periodical dielectric composite structures comprising layers of different dielectric properties have been fabricated as well as multilayered structures containing dielectric and magnetic layers. The measurement results indicate that such multimaterial multilayer structures are good candidates for components with reduced dielectric and magnetic losses. / Tiivistelmä Väitöstyön tavoitteena oli tutkia ruiskuvalettavien 0–3 –liitännäisten keraami-polymeerikomposiittien ominaisuuksia erityisesti niiden GHz-taajuusalueen dielektristen ja magneettisten ominaisuuksien kannalta. Työ on jaettu kolmeen osaan. Ensimmäisessä osassa on tutkittu kaksikomponenttisia keraami-polymeerikomposiitteja, joissa täytemateriaali on joko dielektristä tai magneettista materiaalia. Komposiittien ominaisuuksia on analysoitu jo olemassa olevien seosmallinnuskaavojen avulla. Komposiittien hyödyntämistä erilaisten sovellusten, kuten antennien, minityrisoinnissa on myös käsitelty. Toinen osa käsittelee kolmikomponenttisia komposiitteja, joissa lisäaineena on käytetty pieniä määriä nanomateriaaleja (hopea- ja piipartikkelit sekä alumiinioksidikuitu) tarkoituksena parantaa komposiitin dielektrisiä. Kolmannessa osassa on tutkittu periodisia ja monikerroksisia keraami- polymeerikomposiittirakenteita rakenteita. Kaksikomponenttisten keraami-polymeerikomposiittien tapauksessa suurin permittiivisyyden arvo 15 dielektristen häviöiden ollessa 0.008 (mittaustaajuus 1 GHz) saatiin komposiitille, jossa dielektristä täytemateriaalia (Barium Strontium Titanaatti, BST) oli 37 tilavuus-% termoplastisessa polymeerimatriisissa (ER140). Korkein saavutettu permeabiliteetin arvo 1.8 magneettisten häviöiden ollessa 0.077 (mittaustaajuus 1 GHz) saatiin komposiitille, jossa magneettista täyteainetta (hexaferriitti, Co2Z) oli 43 tilavuus-% ER182 -matriisissa. Tämä täyteaine mahdollistaa nykyistä jopa 77 % pienempien antennielementtien kehittämisen. Tukimuksessa todettiin 2–6 tilavuus-% nanomateriaalin lisäyksen BST-ER140 -komposiitteihin kasvattavan permittiivisyyttä merkittävästi juurikaan vaikuttamatta dielektrisiin häviöihin. Erityisesti 2 tilavuus-% hopeananopartikkeleiden lisäys BST-ER140 -komposiitteihin kasvatti permittiivisyyttä 52 % dielektristen häviöiden (tan δε =  0.004) kasvamatta. Työssä on myös tutkittu periodisesti (vertikaali ja horisontaali) koostettuja dielektrisiä komposiittirakenteita, jossa eri kerroksissa on erilaiset dielektriset ominaisuudet sekä monikerrosrakenteita, joissa vuorottelevat dielektriset ja magneettiset kerrokset. Mittaukset osoittivat, että monimateriaaliset monikerrosrakenteet ovat hyviä kandidaatteja komponentteihin, jotka vaativat pieniä dielektrisiä ja magneettisiä häviöitä.

Pearly layers in seashells, also known as nacreous layers, are reported to be three orders of magnitude tougher than their primary constituent, aragonite. Their high toughness is attributed to a particular structure of alternating layers of natural ceramic and polymer materials. This work tries to emulate it using engineering materials. The thickness, strength, and stiffness of the ceramic layer; the thickness, stiffness, strength, and toughness of the polymer interface layer; and the number of layers are the factors that contribute to different degrees. Furthermore, understanding the relative contribution of different toughening mechanisms in nacre would enable identification of key parameters to design tough engineered ceramics. As a step towards that, in this thesis, layered ceramic beams replicating nacre were studied analytically, computationally, and experimentally. The insights and findings from these studies were then used to develop a new method to make tough layered ceramics mimicking nacre. Subsequently, the use of layered ceramics for armour applications was evaluated. Based on analytical numerical and experimental studies, we observed that the strength of the layers is a key factor to replicate the high toughness of nacre in engineered ceramics. We also demonstrated that, crack deflection and bridging observed in nacre in studies elsewhere, occur due to the high strength of platelets. Based on these findings, the new method developed in this study uses green alumina-based ceramic tapes stacked with screen printed stripes of graphite. During sintering, graphite oxidizes leaving empty channels in the stack. These channels were filled with tough interface materials afterwards. As a result, a ceramic- polymer composite with more than 2-fold increase in toughness was developed. Subsequently, we evaluated layered ceramics for armour applications based on numerical analysis validated with experiments. Consistent to the trends in literature, we observed that layers degrade the resistance to ballistic impact. However, improved energy absorption is demonstrated in layered ceramics. These conflicting dual trends were not presented and quantified in any earlier studies conducted elsewhere. Another new observation not documented earlier is the effect of interface strength. Using an interface material of sufficient strength, penetration resistance of layered ceramics can be improved beyond monolithic ceramics. Using these findings, new layered ceramic armour can be designed that is cost- effective and better performing than monolithic ceramics.

La miniaturisation croissante des systèmes électroniques implique de réduire la taille des composants électroniques, en particulier des composants passifs (condensateurs, résistances et inductances), notamment les condensateurs, volumineux et de surcroît nombreux. Pour répondre à cette attente, une des options est d’intégrer « enterrer » les couches capacitives dans le circuit imprimé à base de matériaux composites céramique/polymère. Dans un premier temps, plusieurs types de matériaux composites à base de nanoparticules de céramique (BaTiO3 et BaSrTiO3) et de polyester pour des condensateurs enterrés sont développés. Ensuite, la permittivité ε’ et les pertes diélectriques des composites sont évaluées dans les gammes de fréquences entre [10 kHz – 10 MHz] et [1 GHz – 5 GHz]. En vue d’intégrer ces composants à l’intérieur du circuit imprimé parfois souple et flexible, le comportement piézoélectrique des composites est évalué. La mesure du courant de fuite permettant d’effectuer une analyse qualitative des matériaux composites a été également effectuée.Au niveau de l’étude des condensateurs enterrés dans le circuit imprimé, deux structures de tests ont été réalisées : l’une montée en parallèle et l’autre en série. L’étude est réalisée sur deux gammes de condensateurs. La première est à base de matériau composite stable en fréquence et la seconde varie avec la fréquence. Pour cela, une méthode originale qui permet d’extraire la variation de la permittivité εr (f) à haute fréquence a été développée. La méthode se repose principalement sur l’utilisation des résultats de mesure de la permittivité relative du condensateur en basse fréquence, et les résultats de la valeur de la fréquence de résonance obtenue en simulation électromagnétique.Enfin, pour améliorer la fréquence de fonctionnement des condensateurs enterrés, des règles de conception permettant de comprendre l’influence des vias de connexions et de la géométrie des électrodes sur la fréquence de résonance du dispositif de test sont étudiées. / The increasing miniaturization of electronic systems involves reducing the size of electronic components, in particular passive components (capacitors, resistors and inductors), including capacitors, large and many more. To meet this expectation, one of the options is to integrate "bury" the capacitive layers based on ceramic / polymer composites in the PCB. In a first step, several types of composite materials based on nanoparticle ceramic (BaTiO3 and BaSrTiO3) and polyester for buried capacitors are developed. Then, the permittivity ε' and the dielectric losses of the composites are measured in the ranges of frequencies between [10 kHz - 10 MHz] and [1 GHz - 5 GHz]. To integrate these components within the PCBs sometimes soft and flexible, the piezoelectric behavior of composites is evaluated. The measurement of leakage current to perform a qualitative analysis of composite materials was also made.At the level of the study of buried capacitors in the circuit board, two test structures were carried out: one mounted in parallel and the other in serial. The study is produced in two ranges of capacitors. The study is conducted on two capacitors ranges. The first case, the relative permittivity does not depend on the frequency while in the second case the frequency dependence is taken into account. For this, an original method which allows to extract the permittivity εr(f) variation in high-frequency was developed. The method is mainly based on the use of measurement results of the relative permittivity of low-frequency capacitor, and the results of resonance frequency value obtained by 3D HFSS electromagnetic simulation. Finally, to improve the operating frequency of the buried capacitors, design rules allowing understand the influence of the vias and geometry of electrodes on the resonant frequency of the structures are studied.